Kinguin is described as 'Marketplace to buy/sell game keys for a myriad of platforms including: Battle.net, EA Origin, Free2Play, GOG.COM, NCSoft, Nintendo, PlayStation 3, PlayStation 4, PlayStation Vita, Steam, Uplay, XBOX 360, XBOX ONE, and others' and is a Game Store in the games category. There are more than 25 games similar to Kinguin for a variety of platforms, including Online / Web-based, Windows, Mac, Linux and Android. The best alternative is Steam, which is free. Other Kinguin like games are GOG.com, GOG GALAXY, Origin and IsThereAnyDeal.
The gaming Client designed for a convenient purchasing, playing and updating DRM-free games, as well as an online play between gaming platforms, GOG GALAXY is also built with optionality in mind, and a belief that you should own the games you...
Very good and clear site for best deals. You can search for current best discounts for a game, set price alerts, looks for historical low prices across multiple stores (not just one) etc. Very customizable alerts.
G2A is an online marketplace (akin to eBay) for video games on a wide variety of platforms such as Steam, uPlay, Origin, Xbox and PlayStation. Both G2A and community members sell a wide variety of games on G2A, at prices which tend to be significantly less then standard prices.